Studies of Contact Hypersensitivity Induction in Mice with Optimal Sensitizing Doses of Hapten

To avoid unsuspected and unwanted consequences of excess hapten during epicutaneous sensitization, optimal sensitizing doses of dinitrofluorobenzene (DNFB) were determined for several ultraviolet B radiation (UVB)–resistant and UVB- susceptible strains of mice. Using these doses of hapten applied epicutaneously or injected intracutaneously into normal or UVB-exposed body wall skin, it was determined that four consecutive daily exposures to UVB prevented contact hypersensitivity induction in all mice when optimal sensitizing doses of DNFB were applied epicutaneously. By contrast, UVB-resistant, but not UVB-susceptible, mice developed contact hypersensitivity when an optimal sensitizing dose of DNFB was injected intracutaneously into UVB-irradiated skin. Moreover, whereas UVB-susceptible mice failed to develop contact hypersensitivity when an optimal sensitizing dose of DNFB was painted on skin exposed to a single dose of UVB, UVB-resistant mice did develop contact hypersensitivity under similar circumstances. Based on these results, it is concluded that 1) conventional doses of epicutaneously applied haptens induce contact hypersensitivity with the aid of antigen-presenting cells derived from both the epidermis and the dermis, 2) the phenomenon of UVB susceptibility is mediated by cells and molecules within the dermis when conventional doses of hapten and UVB radiation are employed, and 3) UVB susceptibility is mediated by cells and molecules within the epidermis when optimal sensitizing doses of hapten and a single exposure to UVB are employed

Iris Pigment Epithelium Expressing CD86 (B7-2) Directly Suppresses T Cell Activation In Vitro via Binding to Cytotoxic T Lymphocyte–associated Antigen 4

A monolayer of pigment epithelium (PE) lines the iris PE (IPE), ciliary body PE, and retina PE of the inner eye, an immune-privileged site. These neural crest-derived epithelial cells participate in ocular immune privilege through poorly defined molecular mechanisms. Murine PE cells cultured from different ocular tissues suppress T cell activation by differing mechanisms. In particular, IPE cells suppress primarily via direct cell to cell contact. By examining surface expression of numerous candidate molecules (tumor necrosis factor receptor [TNFR]1, TNFR2, CD36, CD40, CD47, CD80, CD86, PD-L1, CD95 ligand, and type I interferon receptor), we report that IPE cells uniquely express on their surface the costimulatory molecule CD86. When IPE were blocked with anti-CD86 or were derived from CD80/CD86 (but not CD80) knockout (KO) mice, the cells displayed reduced capacity to suppress T cell activation. IPE also failed to suppress activation of T cells in the presence of cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) immunoglobulin or if the T cells were obtained from CTLA-4 (but not CD28) KO mice. We conclude that iris pigment epithelial cells constitutively express cell surface CD86, which enables the cells to contact inhibit T cells via direct interaction with CTLA-4. Thus, ocular immune privilege is achieved in part by subversion of molecules that are usually used for conventional immune costimulation

AN ANALYSIS OF THE GENETIC REQUIREMENTS FOR DELAYED CUTANEOUS HYPERSENSITIVITY REACTIONS TO TRANSPLANTATION ANTIGENS IN MICE

The experiments reported herein provide ample evidence that mice, like most other mammalian species, are capable of displaying readily observable and reproducible delayed cutaneous hypersensitivity reactions indicative of transplantation immunity. By employing a variety of genetically defined strains, it has been shown that a genetic requirement for the development of a positive normal lymphocyte transfer reaction in mice is a difference between host and cell donor at the H-2 locus. By contrast, the immune lymphocyte transfer reaction consistently reflected the full range of histoincompatibility, both inclusive and exclusive of the H-2. It was incidentally discovered that erythema regularly accompanied delayed cutaneous reactions in the skins of female mice, whereas no local redness accompanied their counterparts in male skins. The influence of cutaneous erythema on the scoring of delayed skin reactions is discussed

A Substance p Agonist Acts as an Adjuvant to Promote Hapten-Specific Skin Immunity

Because substance p (SP) has been reported to be released from cutaneous sensory nerve endings after hapten application, we determined whether SP participates in contact hypersensitivity (CH) induction by using a SP agonist, GR73632 or δ-Aminovaleryl [Pro9, N-Me-Leu10[-substance P7–11 and a SP antagonist, spantide I. When injected intradermally, SP agonist enhanced CH induced by conventional, but not optimal, sensitizing doses of hapten. By contrast, SP antagonist inhibited the induction of CH by optimal sensitizing doses of hapten. Moreover, SP agonist promoted CH induction and prevented tolerance when hapten was painted on skin exposed to acute, low-dose ultraviolet-B radiation. Intradermally injected SP agonist altered neither the density nor the morphology of epidermal Langerhans cells, implying that SP agonist enhanced the generation of hapten-specific immunogenic signals from the dermis. It is proposed that SP is a natural “adjuvant” that promotes the induction of CH within normal skin. Although exogenous SP agonist can prevent impaired CH and tolerance after ultraviolet-B radiation, the susceptibility of native SP to local neuropeptidases renders the neuropeptide unable to prevent the deleterious effects of ultraviolet-B radiation on cutaneous immunity

Origin and Function of Thy-1+ Dendritic Epidermal Cells in Mice

The epidermis of normal mouse skin incorporates a newly-recognized population of dendritic cells which express relatively large amounts of the cell surface glycoprotein, Thy-1 antigen. These cells, termed Thy-1+dEC, are distinct from both epidermal Langerhans cells (LC) and melanocytes, and they populate cutaneous sites in surface densities which range to as high as 580 cells/mm2, approximately two-thirds that of LC. Studies of lethally irradiated mice which were reconstituted with semiallogeneic bone marrow cells and mice which received grafts of semiallogeneic skin have demonstrated that some, if not all, Thy-1+dEC are of bone marrow origin, and that they are capable of migrating into epidermis from a vascular source. Thy-1+dEC expressed both asialo GM1 and a cell surface determinant recognized by the monoclonal antibody 20–10–5S, further suggesting their functions will be included among those normally ascribed to lymphoreticular cells. Isolation of epidermal cells with the Fluorescence Activated Cell Sorter (FACS) was successful in producing relatively pure populations of Thy-1+dEC and LC. Such technological advances as this should facilitate testing several hypotheses concerning the ultimate function of these cells, including the possibilities that they are antigen-presenting cells which selectively activate down-regulating signals, T lymphocytes, natural killer (NK) cells, or natural suppressor (NS) cells

Thy-1 Antigen-Bearing Dendritic Cells Populate Murine Epidermis

Two distinct cell populations, melanocytes and Langerhans cells (LC), have been recognized previously to possess dendritic configuration in normal mammalian epidermis. Employing immunofluorescence microscopy with monoclonal antibodies against Thy-1.2 antigen to identify cells in whole mounts of murine epidermis, we have identified a third dendritic cell population which differs from both LC and melanocytes. Thy-1 antigen- bearing (Thy-1+) epidermal cells are primarily dendritic, although round and angular forms may be found. They are distributed relatively evenly across skin surfaces, although densities vary greatly from site to site and from strain to strain. Densities were highest in ear epidermis from the pigmented strain B10.A (580 cells/ mm2), a value approaching that of epidermal LC, and were lowest in ear epidermis from the albino strain BALB/c (5 cells/mm2). Thy-1+ epidermal cells possess neither Ia antigens nor substantial amounts of melanin, and their surface distributions are disparate from those of both LC and mature melanocytes. We propose that at least some of these cells are T lymphocytes whose malignant counterparts account for cutaneous T-cell lymphomas